Children whose mothers encountered a large amount of air pollution during pregnancy may end up with lower IQs, according to a study appearing in next month’s Pediatrics.

As part of ongoing research, workers at the Columbia Center for Children’s Environmental Health at Columbia University’s Mailman School of Public Health in New York have been following a group of children whose pregnant mothers carried air monitors with them in 2001. The study focused on women living in Harlem and the south Bronx, which have low-income areas often clogged with pollution from heavy car, truck and bus traffic. For this study, researchers tested 140 of the children when they were five years old and found a consistent disparity in IQs. Those who were exposed to high levels of air pollution in the womb (59 percent of the subjects) had IQ scores four to five points below those whose expecting mothers had breathed less polluted air, the authors report.

Some researchers point out, however, that those with lower IQs were also likely subjected to the higher air pollution as infants and also had mothers with less formal education, notes a report by the Associated Press. But others note that the results are part of a growing body of evidence about the impact of everyday pollutants on developing children. “We are learning more and more about low-dose exposure,” Michael Msall, a pediatrician at the University of Chicago who wasn’t involved with the study, told the AP. 

Prenatal exposure to air pollutants has already been found to put children at greater risk for disease, resulting in decreased birth weight and head size as well as a more frequent occurrence of asthma. A study by University of California researchers published earlier this year in Environmental Health Perspectives found that women living in areas heavily polluted with car exhaust were more likely to give birth prematurely than those who weren’t.

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